1. Field of the Invention
The present invention relates to communication systems using elevated platforms (e.g., satellites, orbiting or tethered vehicles, airborne platforms, towers, etc.) for, among other things, a switched relay, and in particular, to the provision of a variable bandwidth, high channel capacity, fully switched, fully interactive communication network operating from a single elevated platform. The inventive system is an optically cross-linked communication system (OCCS).
2. Description of the Related Art
Elevated platforms have been used for radio frequency (RF) communication for years. For example, Cellular telephone systems, Basic Exchange Telephone Radio System (BETRS), Personal Communication Systems (PCS), Geostationary and Low Earth Orbiting (LEO) Satellites, Broadcast Radio and Television (TV) are ubiquitous in our society. In contrast, wide bandwidth systems (typically 1 MHz) have been generally limited to distributive systems (i.e., TV, Direct Broadcast Systems, including DSS, C and Ku band satellite TV systems) or limited to wide bandwidth point-to-point interactive links between a very few (typically 2) points, thereby limiting access to a selected few users.
A typical example is a wide bandwidth point-to-point gateway system, in which a user in Europe communicates to a user in the United States (U.S.) via a satellite positioned over the Atlantic Ocean. The footprint from one of the satellite's beams covers the European user and the footprint from a second beam covers the US user. These wide bandwidth applications exist but are limited presently to a few communication channels.
Some newer "wireless" system designs (e.g., LEO systems such as Iridium, Teledesic, and Globalstar) promise full worldwide interactivity, but they only assure voice capability and other narrowband features, while costing billions of dollars to implement. Typical communication systems have been limited by low bandwidth (typically 10 KHz, sufficient to support 4.8 kilobits/second--kb/sec to 64 kb/sec) because only low bandwidth systems can be fully switched to serve a large number of customers in a fully interactive way. An interesting example of a competing communication system is the U.S. phone system--a "wired" system. It services 130 million lines with fully interactive (switched) 64 kb/sec (about 10 KHz or less of bandwidth) channels. This takes over 20,000 buildings to implement the switching component of the system, and over $200 billion in additional costs for wires, poles, buildings, etc. to implement the "wired" components of the system.
It would be desirable to provide a communication system (or other systems servicing a number of users) that would operate from a single elevated platform that could handle a very large number of customers providing each with fully interactive, switched variable bandwidth (wide or narrow, depending upon user demands) service. Implementing such a system would require a low-cost, low-weight, high performance switch capable of handling digital or analog waveforms, and a variety of multiple access schemes. The application of acousto-optic devices, such as "Bragg Cells," and unique optical switching to provide wide bandwidth, high capacity communication systems from a single elevated platform has not been identified, as far as the present inventor is aware.